Not easy. Kids can bypass very easy. Like those security-theatre apps companies use - but crappier. Then, once on a site/app like Instagram or Roblox it's a whole other layer of whitelist to manage (if possible).

It's simpler to take the phone away. And iPad. And stop hanging out with your friends that have it.

Phone management is hard to solve for pre-teen and teens.

It's like taking heroin away from an addict. They hate you for helping.